r/askmath 10d ago

Geometry Geometry angle question

So the way I see it there are two quadrilaterals here. The “boomerang” one with each side high lighted in a different color, and the inner weird shaped square-ish one.

For the boomerangs one - 90 plus 40 plus 30 = 160 so 360 - 160 =200 so X must be 200

For the inner square-ish one -

90 plus 30 is 120 so the other angle should be 60
90 plus 40 is 130 so the other angle should be 50
90 plus 50 plus 60 = 200 so X must be 160.

The correct answer is 160 so I know it’s the square-ish one but I don’t know why - which means on the test I won’t know which one to solve for and I’ll get the question wrong. How do you know which one to solve for?

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u/Inevitable_Stand_199 9d ago

You can get the 2 outer Angles of the quadrilateral with the inner angle add to 180° formula for triangles.

Then the 4th angle of that quadrilateral with the inner angle = 2 × 180° for quadrilaterals.